The invention relates to an inking unit for a printing machine, including at least one roller, and a metering doctor blade disposed on an ink container and engageable with the roller.
Inking units of the hereinaforementioned type have become known heretofore. They include at least one roller, for example, a screen roller with cells located on the outer cylindrical or jacket surface thereof for accepting printing ink, and a metering doctor blade which, for example, is used for doctoring the printing ink off the roller jacket. The metering doctor blade is attached to an open ink container. During the operation of the inking unit, the level of the printing ink in the ink container lies above the tip and knife or cutting edge, respectively, of the metering doctor blade set against the roller jacket, so that, as the roller rotates, the roller jacket dips into the printing ink and is wetted thereby. It is then doctored off with the aid of the metering doctor blade. During an ink change, or in order to clean the ink container and the metering doctor blade, the container and the blade have to be dismantled and removed from the printing machine. A disadvantage regarding the heretofore known open metering doctor blades is that the level of the printing ink in the ink container must lie far above the tip of the metering doctor blade for attaining a reliable filling of the cells of the roller and, therefore, the ink container and the metering doctor blade cannot be dismantled without an at least brief flowing and dripping, respectively, of the printing ink out of the ink container over the tip of the metering doctor blade. Before the metering doctor blade can be lifted off the roller during dismantling, it is necessary, therefore, for the printing ink level in the ink container to be lowered below the tip of the metering doctor blade.
The published German Patent Document DE 297 18 387U1 reveals an ink fountain or duct with a metering doctor blade attached thereto which, during the operation of the inking unit, is located in a 12 o""clock position with respect to the roller. In order to be able to dismantle the ink duct, it is pivoted through 90xc2x0 into the 3 o""clock position, as a result of which the printing ink stored in the ink duct runs into a channel in the ink duct and is collected therein. The printing ink level in the ink duct consequently falls below the highest point of the metering doctor blade, so that the ink duct can be dismantled without having printing ink run out over the tip of the metering doctor blade.
The published German Patent Document DE 43 37 386 A1 discloses a doctor blade device having an ink container and a metering doctor blade engageable with a roller. Arranged in the ink container are a number of sealing profile strips, which are arranged in an ink chamber containing printing ink, and are adjustable against the roller jacket. In this regard, all of the printing ink is displaced from the ink chamber into a residual space partitioned off from the roller. This occurs at the end of operations or when a temporary operational interruption of the inking unit occurs. The published European Patent Document EP 0 955 164 A1 reveals a similar doctor blade device wherein, in order to empty the ink chamber which is in contact with the outer jacket of the roller, a flexible diaphragm is pressed into the chamber and, in an end position, lies on the roller jacket.
The published German Patent Document DE 26 25 623 A1 discloses a device with an ink container having a wall which is movable linearly in a direction towards a roller and is used for the purpose of exerting pressure on the printing ink in order thereby to counteract the thixotropic behavior of the printing ink and also a nonuniform takeup of the ink from the roller.
It is accordingly an object of the invention to provide an inking unit of the type mentioned in the introduction hereto wherein the metering doctor blade can be arranged laterally on the roller, and wherein the ink container with the metering doctor blade attached thereto is removable from the roller by the shortest route, without allowing any printing ink to emerge from the ink container in the process.
With the foregoing and other objects in view, there is provided, in accordance with the invention, an inking unit for a printing machine, comprising at least one roller, an ink container adjacent to the roller, a metering doctor blade disposed on the ink container and being engageable with the roller, and a movable displacer element for setting a printing ink level in the ink container relative to the metering doctor blade.
In accordance with another feature of the invention, the displacer element is optionally adjustable into a first position, wherein the level of printing ink stored in the ink container lies above a highest point of the metering doctor blade, and into a second position, wherein the printing ink level in the ink container lies below the highest point of the metering doctor blade.
In accordance with a further feature of the invention, the displacer element is formed by an adjustable rear wall of the ink container.
In accordance with an added feature of the invention, the rear wall is pivotably mounted.
In accordance with an additional feature of the invention, the rear wall is pivotably mounted on a base body carrying the metering doctor blade.
In accordance with yet another feature of the invention, the pivotable mounting is on a pivot axis located below a highest point of the metering doctor blade.
In accordance with yet a further feature of the invention, the rear wall has a crank-shaped course.
In accordance with yet an added feature of the invention, in the first position thereof, the displacer element is at least partly immersed in the printing ink stored in the ink container, and in the second position thereof, is lifted completely out of the stored printing ink.
In accordance with yet an additional feature of the invention, the displacer element is pivotable about a pivot axis disposed above a bottom of the ink container.
In accordance with still another feature of the invention, the displacer element has an outer contour matched to an inner contour of the ink container so that a height of a gap formed between at least one of an ink container rear wall and an ink container bottom, on the one hand, and the displacer element moved into an end position, on the other hand, is very small.
In accordance with still a further feature of the invention, the metering doctor blade, in a position thereof wherein it is in engagement with the roller, is disposed, in relation to the roller, below an upper apex and above a lower apex of the roller.
In accordance with still an added feature of the invention, the metering doctor blade is disposed in a region of the roller between 7 o""clock and 11 o""clock positions thereon.
In accordance with still an additional feature of the invention, as viewed in the direction of rotation of the roller, at least one further doctor blade is disposed upline from the metering doctor blade, the further doctor blade being settable in engagement with the roller and serving as a wiper for at least one of air and printing ink.
In accordance with a concomitant feature of the invention, the ink container is trough-shaped, and a cover is disposed on the ink container for closing the ink container.
In order to attain the object of the invention, there is therefore provided an inking unit having a movable displacer element for setting the printing ink level in the ink container relative to the metering doctor blade. With the aid of the displacer element, it is readily possible, as required, to lower the level of the liquid or pasty printing ink in the ink container below the highest point of the metering doctor blade set against or in engagement with the roller. The ink container and the metering doctor blade can then be removed from the roller by a direct route, without allowing printing ink to flow or drip out of the ink container over the tip of the metering doctor blade.
In conjunction with the invention of the instant application, xe2x80x9csetting the metering doctor bladexe2x80x9d onto or into engagement with the roller is understood to mean that the metering doctor blade rests with the tip or cutting edge thereof on the roller cover or is pressed against the latter, so that printing ink located on the roller jacket can be doctored off, or that the metering doctor-blade tip/cutting edge is disposed at a short distance from the roller outer cylindrical or jacket surface, so that a printing ink film with a thickness defined by the gap remains on the roller jacket or a printing material transferred by the latter, for example, a sheet.
When installed in the inking unit, the ink container with the metering doctor blade attached thereto is preferably disposed laterally beside the roller, so that in order to make ready for removal of the ink container from the inking unit and the printing machine, respectively, it is necessary only for the printing ink level to be lowered below the tip of the metering doctor blade, it being possible to dispense with pivoting the ink container into a removal/emptying position, as required in heretofore known devices of this general type. A further advantage of the invention is that the ink container can be removed from the inking unit even with a full printing ink content, for example when production is interrupted, without allowing printing ink to run out in the process. The maximum filling quantity of the ink container, at least when the ink container is being removed, is therefore only sufficiently large so that, at the greatest possible volume of the ink container, which is provided by appropriately positioning the displacer element, the printing ink level lies below the tip of the metering doctor blade.
In a preferred embodiment, the displacer element can be adjusted optionally or selectively into a first position, wherein the level of the printing ink stored in the ink container lies above a highest point of the metering doctor blade, and into a second position, wherein the printing ink level in the ink container lies below the highest point of the metering doctor blade. The first and the second positions can be end positions, the displacer element preferably being adjustable into virtually any desired number of intermediate positions, i.e., infinitely or continuously, or into a limited number of intermediate positions, for example, in a fixed grid or pattern. The configuration according to the invention of the displacer element allows, at least approximately, emptying of the ink container completely, it being possible to ensure a desired inking of the roller even with a minimum quantity of ink in the ink container.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an inking unit for a printing machine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: